This invention relates to film conversion devices which transfer information on film to other media.
The term xe2x80x9ctelecinexe2x80x9d refers to the process of generating a television signal or at least a video signal from cinematographic film, i.e., generally speaking film to video conversion. A telecine machine converts images, and possibly sound and/or other cinematographic information, that are recorded on film into a video format. This video signal may be subsequently recorded on another medium such as on videotape by using for example a video tape recorder film. The resultant video signal, however, may contain ancillary information not recorded on film. For example, in the case where audio is not recorded on the film, an audio signal may be received into an auxiliary input on the telecine machine and incorporated into the video signal produced by the telecine machine. The images are converted into video and supplemented with audio to produce a video signal that includes both images and the sounds. Other information not recorded on film but possibly incorporated into the resultant video signal include e.g., close captioning.
When television first became popular, the state of technology was such that a device to convert images recorded on film into video was quite large and heavy. Since the video tape recorder for storing video electronically was not available until after a number of years of commercial TV broadcasting, the telecine device was designed to be used in a broadcast studio connected to the TV broadcast transmission system. Subsequent designs of full-featured telecine devices have followed the original concept of a large system that is permanently installed.
To transfer film onto video, the telecine device is typically loaded with a spool of film which uses its transport mechanism to move the film across a beam of light. Light that passes through the film is directed through lenses, filters and other optical elements towards a series of sensors that convert optical images of consecutive portions of the film into video signals. Outputs from the sensors are processed in a number of ways to improve or modify the video image, such processors being used, for example, to enhance, color correct, filter, anti-alias, pan and scan, crop and compress the new version of the image. The telecine device provides its data in a particular analog or digital format suitable for storage or further processing or display or conversion into a video signal on an output port and continues to do so until the entire spool of film has been processed or until the telecine operator terminates the process. Some telecine devices are equipped with local memory storage that can hold data corresponding to scanned film frames for reference or for additional processing.
Telecine devices typically operate at a real-time (e.g., 24 frames-per-second) or slower rate. It is common to use 24 frames of film to record one second of motion. The operating rate of the telecine device is typically at or less than the real-time rate, even for films that are recorded at a faster rate than the real-time rate. Devices (i.e., video recorders) coupled to the output of the telecine device expect the telecine device to provide video signals conforming to a particular video standard.
Popular video standards include the National Television System Committee (NTSC) standard in America and Asia, the Phase Alternating Line (PAL) standard in most European countries, and the Sequential Couleur Avec Memoire (SECAM) standard in France. Each video standard defines a particular resolution (i.e., number of lines per frame) and a particular number of frames per second. Each video standard is incompatible with the other. For example, a European video conforming to the PAL standard cannot be played on an American videocassette player or shown on American television that expects the video to conform to the NTSC standard. The timing specifications are different for different video standards. To maintain the proper timing for a desired video standard, the telecine device typically operates at the real-time or slower rate. When the telecine device is operating at the slower than real-time rate, the outputs can be buffered until there is a reasonable collection of video information to start or resume a video recording conforming to the desired video standard. In order to match 24 frames-per-second to NTSC, extra frames are added.
Ancillary information, such as audio and metadata information, is synchronized with the video images. Ancillary information can be provided by the film, a digital file or a peripheral device connected to the telecine device. Pitch converters can adjust the audio speed to match the conversion rate of the telecine device. Film rates and video rates differ. Pitch converters resynchronize the audio with the video so that sound appears to coincide with motion. For example, when 24 frames-per-second film is converted to 29.97 NTSC video, the audio speed must be changed to match the motion in the eventual playback of the resulting video. Some pitch converters can adjust the audio speed in the xe2x88x9225% to +33% range.
The preferred embodiment of the present invention is a high performance film conversion device having a plurality of advantages over conventional telecine devices. The film conversion device has an optical system which is smaller, lighter and also lower in cost to manufacture than prior art telecine devices. A particular feature of the preferred embodiment of this invention is that a subsystem of the film conversion device, namely the optics and film-to-video sensors, is enclosed in a separate module. This feature has a number of significant advantages. The smaller size of the optical system makes it easier than with systems presently available to enclose the main components of the optical system in a dust-free enclosure that also protects the components from external illumination. The small size additionally makes it easier to enclose these components in an electrically isolated environment. The compact size of the scanning subassembly of the preferred embodiment also makes it easier than in the prior art telecine devices to maintain a stable thermal environment for the optical system. One advantage stemming from the removability of the optic/sensor module is improved serviceability of the components of the optical system. The preferred embodiment of the present invention also reduces the interference of the components of the optical system with the path of the film transport.
In the preferred embodiment of the present invention, the optical path of the main subsystems of the optical system is folded substantially into the shape of a xe2x80x9cUxe2x80x9d. This folded arrangement is achieved by placing optical beam bending elements in the optical path of the film conversion device between the illumination subsystem and the film guide subsystem, and between the film guide subsystem and the imaging subsystem. This folded arrangement of the components of the optical system permits the components of the illumination subsystem and the imaging subsystem to be mounted back-to-back on the same support structure within the film-to-video module. Consequently, the optical system requires less space than is required without the folding of the optical path. The reduced size of the optical system and its support structure allows construction of the optical system of a film conversion device that is smaller, lighter, lower in cost, easier to enclose in a contamination-free environment, easier to enclose in an electrically shielded environment, and easier to make thermally stable than the conventional arrangement. An additional advantage of the present invention is that by having the illumination subsystem, the imaging subsystem, and the film guide subsystem arranged on separate segments of the xe2x80x9cUxe2x80x9d shape described above, interference between the optical system and the film handling path of the film conversion device is minimized. The preferred embodiment of the present invention also provides improved serviceability of the optical system by using replaceable windows between the accessible area of the film path and the protected areas of the remainder of the optical components.
Another feature of the present invention is to provide a stand-by mode of operation for a film conversion device in which the lifetime of the illuminating lamp may be extended by turning it off when not scanning film, but that does not require a long delay after powering the lamp for the optical system to stabilize. An additional advantage of the invention permits a film conversion device with an optical system which has improved thermal stability. In the preferred embodiment, this is achieved by placing a heating element near to the illuminating lamp of a film conversion device but not in its optical path. The power dissipated in the heating element is reduced when the lamp is turned on and is increased when the lamp is turned off so as to maintain substantially constant total power dissipation in both situations.
This invention includes a digital parallel-processing core to reduce the time and the cost of a film conversion session. In recent years, digital technology has extended the choices for processing, storing and retrieving information. Video and audio information is stored digitally in computer files, Digital Versatile Discs (DVDs) or Non-Linear Editor (NLE) files. NLE files are manipulated by television and motion picture personnel on computer-based editing workstations in preparation for a distribution or release of a show or motion picture. Digital files reliably maintain their quality and fidelity after many uses. The digital storage methods provide viable commercial alternatives to real-time video processing for the storage, retrieval and transmission of video information.
The film conversion device can operate faster than the real-time rate by processing and assembling an output in a digital format. In the simplest form, a digital file is a sequence of binary data (i.e., ones and zeros). The speed at which the binary data is created does not affect the playback speed. If the binary data is in the proper digital format upon completion of the film conversion session, the information represented by the binary data plays properly on the intended equipment. Therefore, the film conversion device with a digital output can operate at increased rates. By running the film conversion session at faster than real-time, less time is taken to process a spool of film. The total time to convert an entire motion picture is significantly reduced, resulting in cost savings. Furthermore, the output in the digital format can be converter to an analog format by a digital-to-analog converter.
Because of the parallel processing architecture, the film conversion device can simultaneously provide outputs in a variety of analog and digital formats. More time and cost savings are realized as separate film conversion sessions or further processing of outputs are unnecessary to convert film into two or more formats.
In the preferred embodiment, configurable electronics in the digital parallel-processing core provide efficiency and flexibility. Field Programmable Gate Array (FPGA) elements can handle specific repeating operations efficiently while general purpose Digital Signal Processor (DSP) elements provide flexibility. The electronics of the processing core can be chosen to match a particular application, budget or performance. For example, amateurs, students or low budget filmmakers can choose a downscaled version of the film conversion device that provides minimum processing. An upscale version of the film conversion device can provide increased processing power and throughput suitable for delivering high definition video or transferring at rates faster than real-time. The difference between the upscale version and the downscaled version lies in the number of FPGA or DSP elements and the functions they are designed to perform. In one embodiment, different versions of film conversion devices are produced in a factory to meet the needs of different operators. In an alternate embodiment, the operator can add, replace or remove components on the digital parallel-processing core to achieve the desired level of performance.
Digital components generally consume less power and occupy less space than their analog counterparts. FPGA and DSP elements are high-speed devices that can readily adapt to evolving file standards.
In one embodiment, the digital parallel-processing core receives digital data corresponding to film image pixels for conversion to one or more standard formats. Three groups of circuit elements (i.e., FPGA or DSP elements) perform film conversion processing on film image pixels in parallel. A set of two or more film image pixels can also be processed in parallel within each group of circuit elements. In one embodiment, each set of film image pixels correspond to a frame. A memory bank temporarily stores partially film image pixels to ease the timing constraints. A supervisor control circuit communicates with and instructs each group of circuit elements on the processing steps for the film image pixels. The outputs of the digital parallel processing core can be displayed on a video or digital monitor, stored in a local memory, written to a storage medium, or provided to another device for further processing.